The following discussion refers in the first instance to the example of dental implants. For taking an impression of the situation in the patient's mouth and for transferring the impression obtained to a master cast, on which the tooth replacement is then modeled, a number of elements have hitherto been used. The work steps that have had to be performed, and the elements used in these work steps, are dealt with in detail by SCHROEDER, A.; SUTTER, F.; BUSER, D.; KREKELER, G.: Orale Implamologie [Oral implantology], Georg Thieme Verlag Stuttgart, 2nd edition, 1994, page 202 et seq. On the one hand, the assembling of the elements in the patient's mouth, particularly in the area of the molars, is problematic because of the resulting overall height of the elements, especially if a screwing instrument has to be used as well. Moreover, the work procedures are demanding for the patient, and they are time-consuming as regards impression-taking and production of the master cast. In addition to this, inaccuracies occur. The difficulties result primarily from the fact that the impression cap does not hold itself on the implant fitted in the mouth or on the manipulation implant to be used subsequently in the production of the master cast. DE 44 15 670 A1 discloses an impression cap which, at the open end facing the implant, has resilient flaps which, when applied, engage over the shoulder of the conical superstructure, the latter being fitted into the implant. The impression cap described there cannot therefore be used for taking an impression of the implant end protruding from the gingiva and projecting into the mouth, but instead only for taking an impression of the outer contour of the superstructure while the implant is positioned below the gingiva.
U.S. Pat. No. 6,068,478 discloses alternatives to the prior impression/implant systems. U.S. Pat. No. 6,068,478 describes an impression system which comprises as its principal component an impression cap for transferring an end, protruding from a human tissue structure, of an implant which is fitted in the human body, including possible superstructures, to a master cast. The outwardly directed implant end has an undercut contour on its outside, and the impression cap has a geometry which complements the undercut contour and engages therein. The undercut contour is formed either by an implant geometry tapering in a trumpet shape towards the implant bed, or by a recess near the implant end. After the impression cap is secured to the implant, it is encased in impression material. The impression cap embedded in the impression compound present in the impression tray is removed from the fitted implant and receives a manipulation implant to make a master cast.
Two main types of surgical procedures are used in the field to accomplish placement of dental implants in a patient's mouth. In the first procedure, known as single-stage implantation, the dental implant has a threaded portion and a head. A hole is drilled into the underlying bone structure (i.e., the maxilla or the mandible), and the threaded portion is threaded into the hole. The head portion of the implant extends through the gingiva such that the top surface of the head protrudes slightly. The gingiva is then sutured around the head of the implant. After a sufficient length of time for healing, the patient then returns for creation of a master cast.
In the second procedure, known as a two-stage implantation, the dental implant again has a threaded portion and a head. In the two-stage procedure, however, the head of the implant extends slightly above the underlying bone structure and under the surface of the gingiva. After placement of the implant and suturing of the gingiva, the patient is given time for healing. The patient then returns and the gingiva is opened above the implant to allow for placement of an abutment. The abutment employed in the two-stage process has a cuff or base and an abutment post protruding upwardly from the cuff. The cuff is sized such that it ends at a level slightly above the gingiva. Typically, the abutment used in the two-stage process is attached to the implant by threading a screw through a longitudinal bore of the abutment and into the implant. After a further time period for healing, the patient returns for creation of a master cast.
The present invention addresses further constructive alternatives to the prior impression/implant systems. All U.S. patents, patent applications, and other published documents, mentioned anywhere in this application, are incorporated herein by reference in their entirety.